The present invention relates to a touch panel input device, and more particularly to a touch panel input device which can inform an operator of a position where a key will be pressed, before the operator presses the key, to improve the operability of the device.
In conventional touch panel input devices, an operator is informed of the position where a key has been pressed, that is, the position of a key which has been pressed, to detect an error in key operation and an erroneous input operation, thereby correcting such malfunctions.
For example, according to a method disclosed in Japanese patent application JP-A-60-124,724, when a key is pressed by an operator, that area of a display screen which is specified by the key, changes color for a predetermined time, to inform the operator that the key was pressed correctly.
According to the above method, a key operation is checked after a key has been pressed, but no attention is paid to the action of the operator at a time before the key is pressed. In more detail, an angular parallax caused by a gap between a curved display screen and the key input surface of a transparent, flat plate which is laid over the display screen, makes a precise key operation difficult. Thus, an area where a key is effectively operated, is limited, and the possibility of erroneous input operation becomes large as the effective area of the key is smaller.